Knee osteoarthritis is arthritis of a knee joint caused by wear of the cartilage of the knee joint due to various causes such as muscle weakness, aging, obesity. The knee osteoarthritis is a disorder that causes pain and swelling of the knee when the patient moves his/her legs (knees), for example, during walking. Generally, it is said that many Japanese suffer from knee osteoarthritis of a varus type (so-called bow legs), while many Europeans and Americans suffer from knee osteoarthritis of a valgus type (so-called knock knees). Treatment for the knee osteoarthritis is roughly classified into two types, i.e., conservative treatment and surgical treatment. The conservative treatment includes rehabilitation, orthotic therapy, physical therapy, and pharmacotherapy. Shoes for the orthotic therapy, which is an option of the conservative treatment, have been known from, for example, Patent Documents 1 and 2.
Patent Document 1 discloses shoes including an insole with an inclined hindfoot area formed on the back side of the insole. The inclined hindfoot area is located in a range between the foot outer side in an area corresponding to the hindfoot and a straight line connecting a point which is adjacent to the rear end of an area corresponding to the midfoot and adjacent to the foot inner side to a point which is adjacent to the rear end of the area corresponding to the hindfoot and adjacent to the foot inner side. The height of the inclined hindfoot area gradually increases in the direction from the straight line to the foot outer side, so that a surface located on the foot outer side is at a height higher by about 30% than a surface located on the foot inner side.
Patent Document 2 discloses a shoe including a sole (e.g., an insole). An area of the sole, which corresponds to a region, of a foot of a wearer, from the calcaneus to the vicinity of a front edge portion of the cuboid bone, gradually increases in thickness from the longitudinal center line to an outer edge of the sole. Another area of the sole, which corresponds to a region, of the wearer's foot, from the vicinity of the front edge portion of the cuboid bone to the vicinity of a front edge portion of the metatarsals, gradually increases in thickness from the longitudinal center line toward an inner edge of the sole.